The Lincoln experiment
by Laharls Vassal
Summary: Lisa has developed an unfathomable attraction to her brother's scent so the only way to figure this out is with an experiment! Reviews would be greatly appreciated. :)
1. Chapter 1

**The Lincoln experiment**

These unusual and unexplainable feels coursed through Lisa's brilliant mind not long after she had massaged one of his perfect feet during the chaos of trying to get him to decide where the family would go on vacation. Ever since then she had these frequent and bothersome desires to touch his feet again and not just because of how surprisingly smooth they were, the scent emanating from them seemed to be the main reason. The little genius had struggled to conduct her myriad experiments at school and at home because of these thoughts. Also most nights since then she would lie awake squirming at the image of her brother's big feet pressed against her button nose whilst hoping Lily would not hear the occasional involuntary squeak of whine escaping her lips. Luckily for Lisa and the rest of her siblings, the summer holidays were right around the corner so the issue of school work could be cast from her mind for quite sometime so she could use the spare brain power for her predicament.

"Kiiiiiiids, breakfast!" Lynn Loud senior bellowed up the stairs before diving out of the way of the pyjama clad mass charging down to the kitchen.

During the pancakes and syrup fuelled chaos it was not really a surprise that nobody noticed Lisa's absence which is exactly what she wanted and expected even though Leni had previously rushed into her room to bring Lily with them.

"Sweet, simple Leni" she smiled as she started to execute her newest experiment.

The corridor was uncommonly silent but Lisa could still here the cacophony downstairs, the thought of food was crammed to the back of her mind to make room for the fresh pangs of anxiety. All the doors were wide open apart from Lori's, Leni's and of course Lincolns.

"Curse the primitive want of security…" she sighed.

Even though no one could possibly hear her light steps over the noise beneath, she slowly tiptoed anyway and turned the doorknob painfully slowly until the door finally opened. She exhaled heavily, not realising she had held her breath the whole time.

"Get a hold of yourself Lisa!" she admonished. "You're only sneaking into your brother's room, not trying to disprove string theory hypotheses!"

After regaining her composure she looked around the small room and immediately found what she had came in for. A single discarded sock lay on the carpet next to various other items such as Ace Savvy comics and well…more Ace Savvy comics. With a mixture of excitement and timidity she swiftly picked it up, exited his room, closed his door and hurried into her own.

"He won't miss it. This house devours more items of clothing than an echidna devours ants"

Once she locked her door Lisa sat on her bed and gazed at the prize dangling from her fingers. A now familiar feeling wrenched at the pit of her stomach and crawled deep into her pelvic area. With trepidation, Lisa brought the dirty sock to her nose and inhaled deeply. The sense of euphoria she experienced from the scent caused more than just a sense of light dizziness and it seemed like she lost control of her muscles for a moment because she could not stop her body falling back on to her bed.

"F…Fascinating" she uttered staring at the ceiling. "I must conduct further research tonight"

She slid her brother's stinky sock underneath her mattress before joining her family downstairs to involve herself in the chaos which was their daily lives. It was tough but she acted normally around her family whilst sneaking glances at her older brother. Lisa managed to act relatively in character around her siblings for the rest of the day even though waiting for nightfall seemed like an eternity but eventually her patience paid off and after dining on one of their father's delicious meals, bedtime beckoned. After everyone retired to their designated rooms, Lisa set her alarm to midnight knowing that Lincoln would be fast asleep by then. The original plan was to sleep for a few hours before the alarm went off but the anticipation quelled her desire and need to slumber.

"10:48…" she whispered staring at the alarm clock. "I literally cannot wait any longer"

Lisa tossed her duvet aside and was determined to succeed tonight. As quiet as an assassin she silently left her room and entered her older brother's. He was on his back snoring gently much to her relief. With adrenaline filled bravado she carefully lifted the far end of his cover revealing his feet. They immediately captivated her to the point where she had a gormless look on her face. They seemed almost magnetic because she could not stop herself from leaning her face towards them. She pressed her nose against the heel of his left foot and sniffed deeply all the way up to his toes. Once again, euphoria enveloped her senses and she feel to her knees. She winced when she felt the intense tingling sensation down below causing her to involuntary press her hands against her pyjama covered genitalia. After taking a moment to regain her composure she stood back up and stared at Lincoln's perfect feet once more.

"Remarkable…" Lisa whispered.

She desperately wanted to touch them but the shock to her senses had all but decimated her bravery. Lisa exited his room as quietly as she entered without noticing Lincoln opened one of his eyes, a toothy grin spread across his face.


	2. Chapter 2

Once Lisa entered her dark bedroom and had clambered back into her bed, she was still trembling from the experience. She thought about retrieving her brother's stinky sock from underneath her mattress but suddenly the idea seemed torturous because her groin was still tingling to the point where she had to bit her lip to stifle any moans threatening to escape. Lily was fast asleep in her crib so that settled her nerves a fraction but slumber seemed impossible for now, even after she slipped off her glasses.

"How…" Lisa whispered. "How is it that Lincoln's malodorous feet renders me completely idiotic and defenceless?!"

She cursed this weakness that had managed to stop her from thinking about nothing but all branches of science. When ever she tried to think of her beloved pastime, an image of those perfect feet would take over and refuse to leave. Lisa accepted the fact that she would not achieve REM sleep tonight but even though Lisa knew she would be incredibly tired in the morning she still decide to put her current experiments aside and throw herself into the scientific field of biology.

The little genius did not even hear Lori enter the room to retrieve Lily because her body finally gave into the need to sleep during the early hours of the morning. Lori looked at her gently snoring away and did not have the heart to wake her knowing there was no school that day. Downstairs, Lincoln scanned his sisters during the breakfast madness.

"Where the heck is Lisa?" he asked no particular sister.

"Still asleep" Lori replied whilst feeding Lily. "She literally looked sooo cute I couldn't wake here"

Lincoln agreed in his mind and did his best to hide his disappointment. For the rest of the day the siblings indulged in their hobbies. Lincoln lounged in the single chair in nothing but his tight underwear whilst reading his most recent Ace Savvy comic, a common occurrence his sisters had grown accustomed to. He was surprised that Lisa never came downstairs all day, not even at dinner time. His family just rolled their eyes when Lincoln sat down to eat in his underwear but because their father's food was always amazing they were too engrossed in savouring every mouthful.

"Dibs on Lisa's dinner!" Lana yelled immediately after finishing her share.

"Not a chance" replied Rita. "Her food will remain untouched until she is done with her experiments, understood?"

"Yes mom…" Lana sighed.

"Umm…why don't I bring it up to her?" said Lincoln. "You know how she can lose track of time doing her science…stuff"

"Good idea honey but make sure you tell her that she can't keep missing out on family dinner time and for god's sake but your pyjamas on at least"

The snow haired boy chuckled as he took her meal upstairs. He knocked on the door.

"Enter!"

When he opened the door the sight of his little sister frantically writing what he perceived to be complete gibberish on a huge blackboard of all things seemed surprisingly adorable to him. He cleared his throat loudly and could not help but display that trademark grin of his when she involuntarily dropped her chalk at the sight of her big brother in nothing but underwear. Pretending not to notice her reaction, he walked in and placed her meal on her bed.

"It's dad's succotash" he said nonchalantly, sitting on her bed.

"L…Lincoln, why are you parading around in your underwear?!" she stammered.

"I've been reading my comics" he grinned whilst purposely wiggling his toes into the carpet.

He loved watching her try to keep her gaze away from his big feet but also felt a pang of guilt for making her uncomfortable.

"Well…thank you for bringing me my sustenance for the evening Lincoln but…I must press on with my work"

"Okay, I understand" he could not stop smiling. He walked over to her and playfully tapped his finger on her button nose. "Hopefully I'll see you tonight…again" he winked before quickly leaving her room before she could reply.

Lisa's jaw dropped as anxiety clutched at her abdomen.

"He knew?!" she whimpered.

The genius thought she had been as quiet as a shadow. Maybe he was a light sleeper, maybe she sniffed his foot too loudly, maybe the door or floor creaked. She frantically grasped at reasons but she knew, the reason was irrelevant.

That night she was already in bed pretending to be asleep well after Lily had been put in her crib until she was sure everyone had retired to their bedrooms for the evening. Once again in the darkness she crept in to her big brother's room, mainly to find out what he thought of her shameful act rather than attempt it again.

"L…Lincoln?" she whispered in the darkness.

"I was starting to think you weren't gonna show" he replied quietly.

His words startled her and the nervousness only increased when he switched on the dim light of the bedside lamp, a cheeky grin crossing his face. Before she said anything he sat up against his pillows and patted the edge of his bed. Lisa bashfully sat on the bed next to him, his scent already causing her to panic.

"Lincoln…about last night"

He pressed a finger against his little sister's soft lips.

"You don't have to explain Lisa, I'm not mad or anything"

"You're not?!"

He simply shook his head whilst maintaining that heart warming smile, she breathed a huge sigh of relief.

"I still feel like I should apologize. I confess that I do not know what came over me but it seems that the odour emanating from your…your feet drives my senses insane and all rationality and inhibitions take a back seat. Do you understand?"

"I do and if you think about it, it's not your fault because I'm sure that if you had any power over this…let's say issue, then you would not pursue it right?"

"Hmm, you're smarter than I give you credit for"

He chuckled and brought her into a loving hug, rubbing his face in her messy hair.

"Sooo…is it just the smell of my feet that drives you crazy?"

Lisa looked up at him in shock blushing immensely causing him to laugh again.

"Please Lincoln…spare me anymore embarrassment tonight"

"Heh, alright I won't pry any further" he fibbed.

Feeling brave and horny at the same time he removed the duvet covering his body, easily lifted his little sister and placed her between his legs so she was facing him. Lisa's face in the dim light seemed to burn an even brighter shade of red when she noticed that he was just in his underwear instead of his orange pyjamas. His feet were behind her as his legs were laid out straight.

"Wh…What are you doing?" she whimpered feeling those familiar pangs in her groin.

"Well, you're always performing experiments so I thought about trying one of my own"

She was a bit scared but yet again, his smile comforted her.

"O…Okay…I always approve of any and all forms of experimentation"

He giggled at her naivety. He placed his hands on her dainty feet and pushed her further away.

"Take off your glasses"

She obliged by placing them on the top of his drawers.

"You can tell me to stop anytime if you get scared or uncomfortable okay Lisa?"

She nodded preparing herself for the unknown whilst noticing his underwear tenting. Lincoln slowly brought his right leg closer to him and placed his barefoot against her pyjama top, wiggling his toes in the process.

"L…Lincoln…" she blushed.

He teasingly glided his foot up to her face until his toes pressed on her button nose. As Lisa involuntarily inhaled the odour he gently pushed his clammy foot against her face causing her to fall on her back. Lincoln knew he had full control now causing his cock to become uncomfortably constricted in his tight underwear. Lisa moaned as he continued to press his foot on her face. He planned to stroke her skin with his toes but she held his foot in place and sniffed wildly. Lincoln sighed contently as he grabbed his erection after pulling his underwear past his butt.

"Lick'em Lisa…lick my stinky toes" he gasped as he frantically wanked his 4 inches.

The moment her tongue touched his big toe she moaned loudly, the taste of his sweaty and clammy foot sent her into overdrive.

"Heh, Lisa, you've got to keep it down"

"My apologies" she muttered as she snaked her tongue in between his toes.

He noticed that she was grinding against the underside of his leg but was not sure if she was fully aware of it so Lincoln skilfully placed his other foot against her pyjama bottoms and pressed his other big toe against his little sister's virgin entrance as he quickened his hand movement on his cock. Lisa saw stars, a feeling swept over her that could not prevent a throaty moan escaping her eager lips. Worried that his sister would become louder he pressed his saliva coated big toe against her lips and with a little pressure he slipped it into her welcoming mouth. The warm wetness of her tongue swirling around his toe sent a bolt of lust right through him.

"F…Fuck Lisa…I'm not gonna last much longer" he whined as he increased the speed of his hand causing precum to trickle out onto his fingers.

Lisa was not too sure what he meant but the euphoria she was experiencing from his other foot rubbing against her clothed entrance stopped all curiosity. They were both lost in intense pleasure, caution thrown to the wind as Lincoln found he could not contain his lustful whimpers. The little genius removed his big toe from her mouth, a thick string of spit still connecting them before she ran her tongue across all his toes back and forth. This sensation sent Lincoln over the edge to the point where he had to clamp his spare hand across his mouth as he came which also caused him to press hard against his sister's now wet clothed pussy. He breathed heavily through his nose once he climaxed, his cum spurted repeatedly across his stomach, pooling in his navel in the process. With a deep contented sigh he slowed his wanking until had to stop and let the remaining cum coat his hand.

"Lisa…that was…amazing" he giggled stupidly.

With no reply he gazed over at her only to see she was still flat on her back breathing heavily, copious amounts of drool had flowed from the corner of her mouth onto his bedsheets; not that he cared. Lincoln removed his feet from her face and pussy so he could kneel over her. He leaned over and slipped her glasses back on her face before wiping his cum covered body with his duvet. Lisa's eyes seemed glazed over and unfocused; Lincoln was pretty sure she had unknowingly just experienced her first orgasm.

"Lisa…" he waved his hand above her face. "Earth to Lisaaa…"

She blinked rapidly until her focus locked onto her big brother's smile.

"Lincoln…what…what just happened?"

"It's okay, what you experienced was perfectly normal under the…y'know…circumstances. How are feeling?"

"Well…I feel…fascinated, exhausted and…and sweaty"

"Me too" he giggled as quietly as he could.

After regaining control of her body she sat up and smiled at her brother.

"I better get back to my room"

"I guess so…will I see you tomorrow night?" he blushed.

"Of course as you know I always have to see an experiment through to the end"


	3. Chapter 3

The next night, Lincoln was so full of anticipation and lust that he could not prevent his forming erection leaking precum in the same undies he wore yesterday. He did not shower during the day either because he wanted Lisa to experience his natural scent without any pesky traces of soap. He wondered how long he could get away without showering until his sisters complained that he was too stinky to be around.

"That'll be my side experiment" he chuckled to himself.

As expected, his bedroom door slowly opened and he was happy and relieved to see his genius sister.

"Hello Lincoln" she smiled after she closed the door behind her.

"Hey Lisa, are you ready to continue our experiment?"

"Of course, I expect more than stellar results tonight"

"I hope I can rise to the occasion, hop in" he replied, before lifting his covers.

Lisa eagerly climbed into bed with her big brother and immediately his smell assaulted her olfactory senses.

"Shall I start with your malodorous feet again?" she winked.

"Soon…soon, why don't you just cuddle up with me for a while?"

"I don't see what this has to do with the experiment but I have no reason to decline"

The little genius went to nuzzle her cheek against Lincoln's but before she could he, somewhat forcefully cupped his hand in her shaggy hair and pressed her face into his armpit. Lisa began to struggle but the moment she inhaled through her button nose her limbs ceased to work.

"Do you like my stinky armpit Lisa?" he grinned almost malevolently.

There was no reply apart from the noise of his little sister sniffing loudly.

"My god Lincoln…" she uttered. "The scent emanating from your underarm rivals the scent from your feet"

"I'll take that as a compliment" he chuckled.

Lisa wrapped her arms around her brother's slender torso as she nuzzled her face further into his armpit. He sighed contentedly enjoying the closeness but when he felt Lisa's tongue gently press against his hairless underarm he could not resist slipping a hand in his undies and gripping his twitching member. Hearing his little sister moan erotically as she slid her wet tongue around his stinky pit made him quickly glide his hand up and down his length. His pace quickened even further when Lisa started humping his torso, lost in a frenzy of sexual intensity.

"Lincoln…" she whimpered. "Th…This pleasure I'm experiencing is…"

"Is what?" he replied through rapid breathing.

"A little frightening…"

Once again he felt a pang of guilt knowing she was not used to orgasms like he was. From the day he first learned how to masturbate, hardly a night went by where he left his dick alone. He wanted to tell her to power through because the end result would feel spectacular but his brotherly love overshadowed his lust momentarily to the point where he released the grip on his member and embraced her whilst she continued to lick him.

"Lisa, let's stop for a sec"

He pulled her closer so her face slid from his armpit to his chest. Her breathing was erratic so he caressed her unkempt hair until she calmed down. They stayed silent for a little while, both enjoying the closeness even though Lincoln's erection refused to yield.

"Do you know about orgasms Lisa?" he asked, breaking the silence.

"Well, I have the gist I guess. I believe it's the result of experiencing pleasure so intense that the body can not handle so it has to release the pressure through ejaculation. Is that correct?"

"Uhh…yeah that's right. Do you want me to show you on myself?"

"Hmm, I am intrigued, especially since I've been inhaling your odour"

His cock twitched again at that comment.

"Didn't you experience something similar last night when I…you know… pressed my big toe against your…"

"My vagina?"

"Well, yes…"

"I must admit I have never felt anything that pleasurable since I dreamt about meeting Pythagoras and Hippocrates "

He laughed quietly at her statement and hugged her even tighter.

"Alright, this won't take long…thanks to you" he winked.

Without another word he slipped his underwear down to his ankles and flicked them onto the floor with his foot. Lisa's eyes widened once she gazed at his hairless, erect cock. To her it was a glorious sight that made her virgin entrance moisten. When Lincoln gripped his member he slid his free hand from Lisa's hair and snaked it down her lithe frame until it cupped her butt causing her to sigh deeply. Not even a minute later after frantically masturbating, Lincoln could not hold back his grunts and moans. Lisa stared in awe at his cock spurting cum across his torso, a decent amount pooling in his navel. Whilst Lincoln was recovering from his intense orgasm, Lisa sat up and kneeled towards his chest and scooped up a glob her big brother's cum with her index and middle finger.

"So th…this is semen…" she uttered, barely able to contain herself.

Lisa rubbed her cum covered fingers against her thumb, intrigued by the consistency. She then put her finger's up to her nose, a thick string of cum still attached to her thumb. Sniffing the substance confused her olfactory senses, she could not tell if it was pleasant or not. Even though she was hesitant her lust defeated her inhibitions once more so she gingerly stuck the tip of her tongue out and licked. The taste was peculiar, her brain could not make a specific flavour but because a part of her still thought of these antics as an experiment she put her slimy fingers into her mouth so she could properly taste her brother's essence. Lisa found that the taste was delectable and she craved more. Once she had licked her fingers clean she bent down and greedily sucked the cum out of his belly button.

"I'm not scared anymore Lincoln. Please…help me achieve the same euphoria I experienced last night"

The snowy haired boy smiled at her and nodded.

"Climb on top of me and face towards my feet"

Lisa did what he asked and immediately assaulted his toes with her tongue and even though he was feeling extra sensitive he pulled down her pyjama bottoms so her cute little butt was in full view. He would of toyed with her orifices with his cock but because it was not recharged yet, a long slender finger or two would suffice.

"That's it Lisa" he sighed. "Keep sniffing and licking my stinky feet"

He then gently slipped a finger inside her entrance which earned a deep moan as she sucked on his big toe. He pushed it in as deep as it would go and slowly swirled it inside making her move her hips back and forth.

"Does that feel good?" he grinned.

With no response because she still busy slobbering over his feet, he inserted a second finger and began plunging them in and out causing her to tighten her internal muscles. Lisa's moans became more frantic as Lincoln increased the pace.

"It…It's happening!" she whined.

He could feel her whole body tremble uncontrollably and it was only when she collapsed on top of his legs that he slowed the pace down, eventually ceasing all movement. Lisa rested her cheek against his saliva coated toes as she tried to catch her breath, she twitched and whimpered quietly as she felt her brother's fingers slid out of her slick entrance.

"I hoped you enjoyed that as I did" Lincoln chuckled before bringing his slimy fingers up to his lips and licked them clean.

Still unable to speak whilst the waves of euphoria swept over her small frame, Lincoln just caressed her sweaty back and cute little butt until her breathing calmed. After a few more moments Lisa regained use of her body to the point where she shakily lifted herself up, pulled up her pyjama bottoms and crawled over to her older brother's welcoming arms.

"That was beyond remarkable" she whispered, curling up to his lithe frame.

His scent still assaulted her senses but now she was spent, it was more comforting than arousing.

"I'm glad Lisa, I really am" he smiled lovingly whilst stroking her hair.

"Why don't you stay with me tonight…we could tell mom and dad you had a nightmare or something?"

"Capital idea Lincoln" she replied sleepily. "I do not want to be anywhere else but in your bed with you"

He blushed at her uncharacteristic response but was so happy that he silently draped the covers over them and brought his exhausted little sister into a tight embrace, sleep quickly followed for Lisa but it took Lincoln a little longer because of the thoughts of what he wanted to do with her the next day.

"Sleep well Lisa, you're gonna need it" he grinned, kissing her forehead.


	4. Chapter 4

That morning when Lori picked up Lili to bring her downstairs for breakfast she noticed Lisa's bed was empty which was uncommon. She knew that Lisa had slept in their parents bed on a handful of occasions if she was sick or scared but instead of shouting down the stairs she had an inkling to where she might be.

"You'd have to be like, literally stupid to not notice how much time Lisa's spent with Lincoln lately!" she said in a silly voice to the giggling baby.

Once Lori quietly opened her little brother's bedroom door she had to cup her mouth to prevent herself from squealing at the adorable sight before her. Lincoln had such a serene, content smile on his sleeping face. His arms were wrapped around Lisa's tiny frame whilst she snored ever so gently, her mouth slightly agape. Not wanting to disturb them she closed the door and began the morning routine, not before taking a quick picture on her treasured phone of course.

The light click of the door being shut interrupted Lisa's slumber. She blinked rapidly at the harsh rays of daylight bombarding the room. Lazily rubbing the sleep from her eyes she was about to get up and get ready for the day until she remembered she was not in her own bed. Something similar to anxiety gripped her abdomen when she noticed her brother's arm draped over her but after quickly remembering what they experienced last night, a smile spread across her face. The tiny genius turned her body so she was facing Lincoln. Her heart raced when she stared at her sleeping brother.

"So perfect…" she whispered.

He was on his back and Lisa could tell by his rhythmic breathing that he was still in a deep sleep so she took a sneaky whiff of his hairless armpit. As expected, the scent forced a greater smile on her face as she shuddered involuntarily. Feeling brave and horny she shuffled underneath the covers until her face was very close to her brother's flaccid penis. She stared at it for a while, completely mesmerised. After the fun her and Lincoln had experienced she knew he would not mind if she experimented. Taking a deep breath, Lisa brushed her fingers against his manhood, the smoothness pleased her. She lightly gripped his foreskin between her index finger and thumb, fascinated by the feeling. it was then when she remembered him gripping his cock and shaking it like you would a ketchup bottle to get the last dollops out so she decided to attempt it herself. Not wanting to wake him abruptly, Lisa gently wrapped her tiny hand around his shaft and slowly began to rub up and down. There seemed to be an immediate change in Lincoln's breathing but she was so hypnotised by his cock growing rapidly up to the point where she could barely wrap her hand around it.

"Intriguing" she muttered, feeling self-control waning.

When it became hard to the point where it was twitching she noticed his foreskin had stretched exposing his slit. Lisa nerves caused her to shake a little but she wanted to go further so with a little force she reinforced her grip and pulled the skin down, exposing his pink helmet. Her eyes widened at the beautiful sight and with out any trepidation she pressed her nose against it and inhaled deeply. A mixture of Lincoln's sweat, and dried cum caused an audible sigh, her warm breath causing him to stir. He slowly began to awaken when Lisa quickly increased the pace of her hand the moment his scent took over. She remembered how his semen tasted and suddenly she became desperate to taste it again.

Lincoln was fully awake now and he had to bite down on his lip to stifle his moans as his little sister made precum leak out onto her dainty fingers. The pleasure abruptly came to a halt, frustrating him. He could not see her because she was fully under the covers so he could no longer keep up the pretence of being asleep if he wanted to know why she stopped. He gripped his covers and ever so slowly lifted them to reveal Lisa sensually licking her fingers clean.

"Good morning Lisa" he beamed with those adorable front chipped teeth.

"G…Good morning Lincoln" she stuttered.

"Why'd you stop?"

"I…uhh…I apologize, I was just intrigued by the fluid you excreted because it's different from last night" her cheeks became crimson with embarrassment.

"Don't apologize" he laughed. "That's called precum, it's the stuff that comes out before semen.

"Ahh…on some level, I knew that"

Her naivety was adorable to him but his cock still demanded attention.

"Why don't you try putting it in your mouth…just the tip?"

Her eye's widened at the suggestion.

"Wouldn't that be a little…unhygienic?"

"But slobbering over my stinky feet isn't?"

"Huh…a valid point"

The idea had entered her mind the moment she sniffed his cock but she was unsure what his reaction would be so the act of uncertainty was sophistry, nothing more.

"No pressure, It's-"

Lisa wrapped her eager lips around his precum coated tip before he could finish that sentence making him inhale sharply. This blew her mind and at that moment she knew that she probably would not be able to go a day without experiencing the taste of her big brother.

The urge to grip her hair, shove his full length into her mouth and relentlessly hump her face was so great but once again, annoying brotherly love intervened. He knew she had never done anything like this before and as this was his first blowjob he had ever received so he did not want to ruin what they were both experiencing.

"Th-That's amazing Lisa…" he breathed heavily.

The little genius's tongue slowly swirled around his exposed helmet, savouring the scent and taste. Lincoln knew he would not be able to last long after witnessing her sample his precum.

"St-stop Lisa…otherwise I won't be able to hold it back!" he warned.

His words only made her more eager so she took a little bit more of his length in her mouth and increased her tongue movements from gentle swirling to wild flailing. The intense pleasure was too much for Lincoln. He had to dig his fingers into his mattress to prevent him from pushing her head down during his climax. Lisa's eye's widened when she felt thick ropes of her brother's cum hit the back of her throat. The amount forced her to release his spasming cock from her warm mouth, the last spurts coated her glasses and cheeks. She coughed weakly as strings of her brother's warm essence leaked from her mouth onto her pyjamas. Once Lincoln had recovered from one of the best orgasm's he had ever experienced, he was mortified to see her dripping face.

"Oh my gosh! I'm so sorry Lisa…I couldn't control myself!"

"Worry not sibling" she replied before removing her spectacles and slowly running her tongue across the lenses, savouring his taste of his thick cum.

"You warned me but I opted to continue…only for the sake of the experiment, of course…" she blushed.

Not saying anything, Lincoln pulled her into a loving hug as he used his pyjama sleeve to wipe the remnants of his essence from her angelic face. For a moment she wanted to inform him that she too wanted to experience relief but for the sake of the experiment she decided to see how long she could contain her urges but with a perfect specimen like Lincoln she knew her loins would not rest long.


	5. Chapter 5

Lisa's sexual frustration refused to leave her during the day and at one point she announced to her family that her mind had a scientific breakthrough so she required an uninterrupted session with the blackboard in her and Lily's room. Knowing that they always respected her privacy she did not hesitate to whip her big brothers stinky old sock from underneath her mattress and pressed it against her button nose. She inhaled deeply, the wave of smells and euphoria caused her to whine.

"Curse your smell Lincoln…" she whispered, both loving and hating the control it had over her.

Remembering that he used his fingers to pleasure her whilst she worshipped his perfect feet, she hesitantly slipped her hand into her panties. Her trembling middle finger gently pressed against her moistening entrance and slowly slipped the tip inside causing her to shudder. The genius bit down on her bottom lip as she slid it further inside. Swirling it around in a circular motion felt amazing, especially with the constant stink from her big brother's sock assaulting her senses every time she inhaled. Every time Lisa shoved her middle finger inside up to the knuckle, the tip of her index finger tapped her clit which caused even more intense feelings so after quickly figuring this out she pressed hard against her little rose bud which increased the pleasure infinitely. The combination of rapidly plunging her middle finger inside whilst frantically swirling the other one against her clit and sniffing Lincoln's crusty sock made her experience an orgasm nearly as great as the one he gave her. Her body involuntarily bucked repeatedly until the orgasm waned. Once her muscles relaxed she brought her fingers up to her nose and gave a quick sniff before licking her own juices from them.

After taking an apt amount of time to regain her composure and concealing his stinky she headed back downstairs to tolerate her siblings before another magical night with her brother. Lisa scanned the living room as she headed downstairs but Lincoln was nowhere to be seen. Lori was on the sofa, glued to her phone as usual. Surprisingly she was the only one in the living room right now, the rest were outside or in their rooms. Lisa sat on the sofa next to her eldest sister and endured thirty seconds of the love boat before she decided to interrupt Lori's text messages to who she assumed was boo boo bear.

"Lori, do you have any idea as to the whereabouts of our brother?" the genius asked nonchalantly.

"He went to ride bikes with Clyde" she replied without looking up from her phone.

"Hmm, do you know when he will return?"

"Who cares?" she retorted. "Lately he's been stinking up the place worse than Lynn and Lana combined!"

Lisa could not disagree but it seemed that she was the only sister that craved his scent which bamboozled her but, one experiment at a time. As she headed back to her room to ponder why she was the only one that wanted him to never shower or bathe again she suddenly realised how stinky he would be after a long bike ride, especially his feet.

"Could he be doing this for me or are his actions a result of the desire for male companionship, or both?"

Either way, Lisa struggled to keep her newly discovered libido in check. For the rest of the afternoon all Lisa did was tinker with her chemistry set whilst impatiently waiting for her brother's return.

Once dusk had settled and Lincoln still had not come home, her anxiety at the thought of him deciding to stay over at Clyde's for a sleepover kept growing. Lisa snapped out of her funk when Luanne sat next to her on the sofa with a thump before draping an arm around her little sister.

"Hey Lisa!" she smiled as she briefly tickled her earlobe and then displayed a coin before her eyes. "Penny for your thoughts?" the comedienne chuckled loudly.

Lisa sighed audibly but a little smile appeared because it seemed that Luanne was concerned about her.

"Oh…nothing really"

"You expect me to believe there's nothing going on in that big brain of yours?" she giggled while gently tapping her knuckles against her head.

"Well, if you must know…I'm just a little concerned with the whereabouts of our brother as he is out later than he usually is."

"You mean Stinkoln? Hahaha!"

Lisa quickly looked up at her older sister with an annoyed expression but then quickly turned away when she felt her cheeks flush. Luanne placed a hand on her shoulder and smiled warmly.

"Don't worry so much Lisa, you know he wouldn't miss his curfew"

"So…you think he's staying over Clyde's house?" she mumbled, still looking away.

"Nah, he would have told at least one of us, if not, he definitely would have told mom and dad" she reassured.

"Hmm, I suppose so"

"You two have become really close lately haven't you?"

"Well…he is our only brother…" she replied, her cheeks burning even brighter.

Luanne squeezed her shoulder lightly, completely oblivious to what was going on between them.

Lisa thanked Luanne for making her feel a little better and not long after, their father announced dinner time. She had to admit that even though anxiousness continued to annoy her, she was starving and judging from the smell beckoning everyone to the kitchen, it was lasagne night; which nobody could pass up. They noisily devoured the food as a family but it was only Lisa that first noticed her brother in the kitchen doorway. He greeted everyone as he removed his bicycle helmet. Most of them mumbled some form of greeting with their mouths full without paying any attention. Lisa was the only one that noticed the sweat drenched underarms of his orange shirt as he unbuckled his helmet. His snowy hair was damp with sweat, clinging to his forehead. He gave Lisa a cheeky wink knowing that tonight would be incredible.

"Lincoln!" his mother exclaimed. "You barely made curfew, you're dinner has gone cold"

"I still made it didn't I? Besides, I had dinner at Clyde's house"

"Well that means that you'll have cold lasagne for your breakfast!"

"What a shame…" he chuckled before heading upstairs.

Lisa quickly devoured her meal in a desperate attempt to be the first upstairs. The fact that her family might suspect anything was not something she even considered because of the lust that had overtaken her mind. Once she thanked her father for the delectable meal, Lisa quickly exited the kitchen and ascended the stairs, leaving her sisters to babble amongst themselves. Lisa ascended the stairs quicker than she ever had before, only to find one of Lincoln's iconic orange t-shirts at the top. She automatically knew that is was the t-shirt he had worn today before gripping and burying her face into the sweat drenched underarms. Forgetting her surroundings, she loudly sucked at the wet spots, savouring every salty drop of his sweat that dripped on to her tongue.

"You would be so easy to trap in the wild" Lincoln sniggered.

Lisa's mouth did not leave the sweaty garment as her eyes looked up at her shirtless brother grinning at her from his bedroom door with those pearly chipped front teeth. Lincoln beckoned his little sister into his room with his index finger and like a starving hound clapping her eyes on a prime steak, she raced towards her big brother, shirt still gripped between her teeth. The moment he shut his bedroom door, Lisa let the garment drop to the floor before leaping into his sweaty chest. He caught her by cradling her cute little butt. He could not resist giggling a little as she buried her face in his sweaty armpit, sniffing, licking and moaning wildly.

"C…calm down Lisa" he managed to utter. "You're making me hard!"

She completely ignored him as she continued to assault his stinky underarm with her tongue. His pants became tighter as his erection grew but he could not release it whilst he held his horny little sister. Much to her dismay he walked over and dropped her on his bed but she perked up when she witnessed him quickly remove his jeans and briefs, revealing his engorged member. Knowing they should be quick just in case one of their siblings decided to come into Lincoln's room for whatever reason after finishing their meal, the snowy haired boy clambered on top of his sister and smashed their lips together. Even though he could taste his own sweat, he gripped her scrawny arms and thoroughly explored her eager mouth. He actually kind of liked his own taste on her soft lips. His lust felt so aggressive that he wanted to rip her clothes off and fuck her relentlessly right then and there.

"Do you really wanna make me cum now? What about tonight?" he asked after he released their lip lock to regain his breath.

"Logically speaking…" she uttered, looking up at the embodiment of perfection. "Once you experience an orgasm after this encounter you second orgasm should take longer to achieve"

"How do you know that?!"

"I've mastered biology, if you want me to tutor you for your upcoming exam on the field, I will be more than happy to oblige" she winked.

Once again, Lincoln had to supress his urge to fuck her until they both lost touch with reality. Instead, he manoeuvred himself into a 69 position so his sweaty, hairless ball-sack rested on her button nose whilst he grinded his precum covered cockhead against his little sister's soft lips. Lisa eagerly engulfed his leaking member as she deeply inhaled his scent. Her warm and wet mouth enveloping his twitching cock caused a shudder through his lithe frame to the point where he wanted her to experience the pleasure she was giving him. He easily pulled her pants and underwear down to her ankles, exposing her bald pussy. Wasting no time, he quickly inserted his index and middle finger into her moist hole, her moans of pleasure vibrated against his cock. He wanted to give her equal pleasure before he exploded inside her mouth so he removed his fingers and licked her juices from them before placing his mouth over her slit. He began to move his tongue slowly between her tight flaps causing her to whine deeply as she continued to suck his delicious cock. There was no way he could prolong this intense experience any longer so he sped up the pace of his hips as he continued to fuck his little sister's face.

"L…Lisa…" he sighed as he took a breath from servicing her tight pussy. "I'm….I'm gonna cum…!"

The genius showed no plans to slow down her assault on his pulsating cock so he continued to delve his tongue into her leaking entrance, concentrating on her clitoris with the tip of his tongue. In an untamed frenzy of humping each other's mouths, the siblings involuntarily increased their speed almost to the point that their sweaty bodies were almost a blur. Lincoln was the first to unleash his cum down Lisa's throat, luckily his guttural moans where muffled by her now dripping entrance as her body joined his in the throes of an intense orgasm. They continued to hump and breathe heavily for a few seconds before their orgasms caused their genitals became too sensitive. Lincoln collapsed on top his little sister with a goofy look on his face as she lazily slid her tongue back and forth on his slimy cockhead until it slid from the corner of her drooling mouth, coating her cheek with the remnants of her big brother's essence that she could not swallow.

"Wow, Lisa…" he chuckled giddily. "You're definitely my favourite sister…"

Lincoln lazily clambered off of her and positioned himself so they laid face to face.

"Was there ever any doubt that I wasn't?" she grinned as she wiped her cheek and mouth with the back of her hand.

They shared a quiet giggle as she snuggled up against him and mashed her face into his sweaty armpit once more.

"You know I would like to spend all night together like this Lisa, but it's not bedtime yet"

"Worry not, just give me a minute to completely gather my bearings then I shall join our siblings in our regular evening activities before bedtime" she winked.

"Good thinking" he smiled. "I better stay in my room and read comics though, so they don't complain about how stinky I am"

"Capital idea Lincoln. This may be the last night I can enjoy your scent before our parental units literally force you into the shower"

The siblings both shared a chuckle before he pressed his lips against hers. After their tender kiss, Lisa reluctantly left her big brother's sweaty bed, pulled her underwear and pants back up and left his room with a naughty little wink. The moment his door shut, Lincoln laid back on his bed, still grinning goofily even though he knew the next few hours would seem like a lifetime, even if he was reading his ace savvy comics.


	6. Chapter 6

Finally, bedtime beckoned. Lincoln listened to the chaos of his sisters sharing the bathroom for their usual nightly routine. His erection refused to wane because he planned to go all the way with his genius sister tonight. The stampede eventually lowered in volume as his sisters retired to their bedrooms. The symphony "ode to joy" played in his mind once he heard all the doors close even though he knew he would have to wait at least another half an hour before Lisa would risk sneaking into his room.

"Down boy, be patient" he whispered as he repeatedly tapped his rock hard member over the covers with his hand.

Not surprisingly, this did not work. It felt like an eternity before he heard his door creak open gently. Once Lisa entered and quietly shut the door behind her, he quickly lifted up his cover and beckoned her towards him with his index finger. Lisa leapt into his bed, the sheets were still a little damp from their crazed session earlier that evening.

"Glad you could join me" he winked, beaming those pearly chipped front teeth.

"Not as glad as I am" she replied with the same smile she had when she saw Lincoln's British tutor.

He chuckled quietly before leaning forward and pressing his lips against hers. They shared a sloppy but passionate kiss for quite some time until Lisa broke it to lick his sweaty, hairless armpit. He ruffled her shaggy hair with his hand whilst stroking his hard member with the other.

"Lisa…do you want to try…sex?"

The genius stopped licking and looked up at him with anxiety in her expression. "I don't know Lincoln…using quick mental arithmetic, I do not see how it would be possible for your phallus to fit inside my vagina…"

"Well…what's the point of creating a hypothesis without testing it?" he beamed smugly.

Thanks to the moonlight shining through his window, Lincoln could see his little sister's eyed had widened at his comment.

"Haha, what?" "I listen to your gibberish occasionally" he winked.

"V…Very well Lincoln…" she stuttered, still a little scared. "You sure know how to get a girl's gears going"

"Heh heh, do you want me to continue?"

Before he could think up any other fancy scientific terms, Lisa removed her pyjama bottoms before further exploring her brother's mouth with her tongue again. Eventually, he reluctantly pulled himself away. As they both took the opportunity to get their breath back, he clambered on top of her tiny frame, his rock hard erection rubbing against her inner thighs. He gently grazed her virgin entrance with his leaking cockhead which caused her to yelp involuntarily.

"It sounds like I'll have to find a way to keep you quiet" he grinned.

Picking up another one of his stinky discarded socks off the floor, he cockily manoeuvred himself forward so the tip of his cock was directly above her mouth. He kept his dirty sock in his hand, just in case.

"Help me get my cock wet. It'll help both of us"

Lisa was more than happy to oblige. She gripped his erection with her dainty hand so she could deeply inhale the sweaty scent from his hairless testicles against her button nose. Her pupils nearly went into the back of her head after she inhaled his sweat, her body quivering in the process.

"You okay, lisa?" he asked with genuine concern when he saw her shaking.

"M…More than okay…" she uttered in a state of euphoria.

He beamed proudly at the fact that his natural scent could render the little genius helpless. He decided to help out by guiding his slimy cockhead against her inviting mouth. Without any hesitance, he slid the tip inside. He inhaled sharply as her mouth wrapped around it in a warming embrace. Knowing that he could only enjoy her flailing tongue for a few seconds because he would explode in her mouth, he quickly pulled out of her drooling mouth and got into the vital position.

"Are you ready…?"

"R…Ready as I'll ever be"

"Just remember to tell me if it's too much, I don't want to hurt you"

The fact that her big brother showed concern and affection for her made her feel more willing and at ease. She truly loved him as much as he loved her.

Realising it might still be too big for her virgin entrance, he circled his index and middle fingers in her mouth. He knew that she made more saliva than anyone in the family so it made it much quicker for him to remove his fingers and gently swirled them around her hairless entrance. He earned a little whimper when he inserted his fingers inside her. He slowly pushed them around inside, causing her to squirm with pleasure. Each moan and yelp made his cock twitch.

"Lisa, I've gotta do it know…my dick isn't too much bigger than my fingers…I'll go slow…I promise" he beamed with reassurance which hid his desperation.

"O…Okay Lincoln… I'm ready" she uttered.

He could tell that she was nervous by her tone so he had to make good on his promise. He gently kissed her face all over as he manoeuvred himself so his dripping cock pressed against her entrance. He straightened his arms next to her head and slowly pressed his precum coated head inside his beloved sister. She whimpered quietly once his tip slipped inside her.

"You okay?"

"Y…Yes…"

He gave Lisa a heart warming smile before he pressed his lips against hers as he gently slid his whole length inside her. Her brother's cock did feel uncomfortable and invasive for a few seconds but he lovingly manoeuvred his hips back and forth ever so slowly so the pain eventually gave way to pleasure. He kept peppering her face with loving kisses as he gradually increased the speed of his hips thrusting in and out of his sister's no longer virgin entrance. The warmth of her inner walls rhythmically tightening against his cock involuntarily caused Lisa to moan loudly so Lincoln decided to gag her with the stinky sock he held in his hand. The scent and taste of her big brother's sock assaulted her taste buds and olfactory senses immediately, causing her to groan even more. The cheesy, salty taste of Lincoln's sock caused her to experience an otherworldly level of pleasure as he rapidly slammed himself into her.

"Ohhhh god Lisa…I'm not gonna be able to last much longer!" he uttered.

Lisa tried to say that she was also dangerously close to orgasming but because her big brother's crusty sock filled her mouth, she could only mumble incoherently. The muffled sounds she emitted as he slammed himself into her forced him to bite his bottom lip. Knowing he could not hold back much longer, he hooked his arms underneath her armpits so his hands gripped the back of his little sister's shoulders as he increased the speed of his thrusts. His hips acted like pistons, the obscene noise of their wet genitals rapidly slapping against each other in the silence of the night heightened his the pleasure.

"G…Get ready Lisa…" he managed to utter.

The snowy haired boy's moans became guttural and aggressive as the speed of his thrusts into his little sister's tight pussy almost became a blur. Caution was thrown to the wind, his dirty sock barely muffled her squeals and the bed rocked furiously until Lincoln finally erupted inside her. He quickly snatched his sock out of her drooling mouth and threw it onto his bedroom floor before crushing his lips against hers, not minding the taste of his toes on her flailing tongue whilst he continued to spurt copious amounts of his boy cum deep inside. Lisa whimpered loudly into his warm mouth as the warmth of his hot semen shooting into her entrance made her frail body experience multiple orgasms. Eventually his thrusts waned as all his energy was spent. Once the last lot of cum seeped into his little sister's pussy, he collapsed on top of her still quivering frame. Breathing heavily, rapidly and stinking of sex and sweat, the siblings chuckled giddily.

"Th…That was amazing…" he whispered into her ear.

"I…I concur…" was all she could muster.

They became silent for a few moments to catch their breath. Her big brother's scent became comforting instead of arousing once again even though it was still overpowering. He went to pull out of her slick entrance but she quickly wrapped her arms around his sweaty back.

"Please don't take it out" she whispered, glad that the darkness hid her crimson cheeks. "C…Can we stay like this until I inevitably fall into slumber?"

Lincoln giggled as she nuzzled her face into his armpit.

"Fine by me Lisa…Fine by me"

After a while, both could barely keep their eyes open, the warmth on their genitals still merged together was the only reason they temporarily waylaid the sandman.

"Hey Lis…" he mumbled.

"Hmm…?"

"Does what we did tonight mean you've finished your experiment?"

"Well…" there was a brief silence.

"Any scientist worth their salt would attempt their experiment again and again until the desired conclusion has been achieved"

Lincoln giggled sleepily.

"And how long do you think that will take, professor?"

"Ohh, at least a few years"

Grinning in the dark, he gently kissed her lips, keeping his promise to remain inside her. The siblings finally succumbed to exhaustion and fell asleep as one.


End file.
